U.S. patent application Ser. No. 13/090,616, U.S. Pub. No. 2011/0263627, describes inter alia certain N3-substituted-N1-sulfonyl-5-fluoropyrimidinone compounds and their use as fungicides. The disclosure of the application is expressly incorporated by reference herein. This patent describes various routes to generate N3-substituted-N1-sulfonyl-5-fluoropyrimidinone compounds. It may be advantageous to provide more direct and efficient methods for the preparation, isolation, and purification of N3-substituted-N1-sulfonyl-5-fluoropyrimidinone fungicides and related compounds, e.g., by the use of reagents and/or chemical intermediates and isolation and purification techniques which provide improved time and cost efficiency.
Provided herein are 5-fluoro-4-imino-3-(alkyl/substituted alkyl)-1-(arylsulfonyl)-3,4-dihydropyrimidin-2(1H)-one and processes for their preparation. In one embodiment, provided herein is a process for the preparation of compounds of Formula III:
wherein R1 is selected from:
and R2 is selected from:
which comprises contacting compounds of Formula II with a base, such as an alkali carbonate, e.g., sodium-, potassium-, cesium-, and lithium carbonate (Na2CO3, K2CO3, Cs2CO3, and Li2CO3, respectively) or an alkali alkoxide, for example, potassium tert-butoxide (KOtBu) and an alkylating agent, such as an alkyl halide of Formula R2—X, wherein R2 is as previously defined and X is a halogen, e.g., iodine, bromine, and chlorine, in a polar solvent, such as N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), acetonitrile (CH3CN), and the like, at concentrations from about 0.1 molar (M) to about 3 M. In some embodiments, a molar ratio of compounds of Formula II to the base is from about 3:1 to about 1:1 and a molar ratio of compounds of Formula II to alkylating agent is from about 1:1 to about 3:1. In other embodiments, molar ratios of compounds of Formula II to the base and compounds of Formula II to the alkylating agent a about 2:1 and about 1:3, respectively, are used. In some embodiments, the reactions are conducted at temperatures between −78° C. and 90° C., and in other embodiments, the reactions are conducted between 22° C. and 60° C.

It will be understood by those skilled in the art that manipulation of the reaction parameters described above may result in the formation of product mixtures comprised of compounds of Formulas II, III, and IV, as shown in Scheme 1, wherein the ratios of compounds of Formulas II, III, and IV formed is from about 0:2:1 to about 1:2:0. In some embodiments, compositions comprising mixtures of compounds of Formulas II and III are preferred, as isolation and purification can be achieved through precipitation and recrystallization, and the intermediate compounds of Formula II can be recovered and recycled. In contrast, compositions comprising mixtures of compounds of Formulas III and IV require chromatographic separation to give III along with the undesired dialkylated by-product of Formula IV.

In another embodiment, the desired crude composition, i.e., mixtures of compounds of Formula II and compounds of Formula III, wherein R1 is methoxy (OCH3) and R2 is methyl (CH3), is obtained through contacting a compound of Formula II with Li2CO3 and methyl iodide (CH3I) in DMF (1.0 M) in a molar ratio of about 1:0.6:3 at 45° C. Upon completion, dilution of the crude composition with a polar, aprotic solvent, such as CH3CN, wherein the ratio of CH3CN:DMF is from about 2:1 to about 1:2, followed by an aqueous solution of sodium thiosulfate (Na2S2O3) with a pH from about 8 to about 10.5, wherein the ratio of 2.5 wt. % aqueous Na2S2O3:DMF is from about 1:2 to about 3:1, affords a precipitate which is isolable by filtration. In one embodiment, the ratio of CH3CN:DMF is about 1:2 and the ratio of 2.5% aqueous Na2S2O3:DMF is about 1:1, and the resultant solid is further purified by crystallization/precipitation from a warmed solution, about 30° C.-40° C., of the solid h a solution of a polar, aprotic solvent, such as CH3CN, by the addition of water (H2O), wherein the ratio of H2O:CH3CN is from about 1:2 to about 3:1, to give the purified compound of Formula III, and in another embodiment the ratio of H2O:CH3CN to affect precipitation of pure III is about 2:1.
In another embodiment, compounds of Formula II may be prepared by contacting compounds of Formula I with bis-N,O-trimetliyisilylacetamide (BSA) at an elevated temperature, such as 70° C., for a period of about 1 hour (h), followed by cooling and contacting the solution containing the protected pyrimidinol with a substituted benzene sulfonyl chloride, generalized by R1—PhSO2Cl, wherein R1 is as previously defined, at 20-25° C. In some embodiments, the molar ratio of the compound of Formula I to BSA and the sulfonyl chloride is about 1:3:1.1, respectively, and in another embodiment reducing the molar ratio of the reactants to about 1:1.1:1.1 affords improved yields.

The term “alkyl” refers to a branched, unbranched, or saturated cyclic carbon chain, including, but not limited to, methyl, ethyl, propyl, butyl, isopropyl, isobutyl, tertiary butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.
The term “alkenyl” refers to a branched, unbranched or cyclic carbon chain containing one or more double bonds including, but not limited to, ethenyl, propenyl, butenyl, isopropenyl, isobutenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, and the like.
The term “aryl” refers to any aromatic, mono- or bi-cyclic, containing 0 heteroatoms.
The term “heterocycle” refers to any aromatic or non-aromatic ring, mono- or bi-cyclic, containing one or more heteroatoms.
The term “alkoxy” refers to an OR substituent.
The term “halogen” or “halo” refers to one or more halogen atoms, defined as F, Cl, Br, and I.
The term “haloalkyl” refers to an alkyl, which is substituted with Cl, F, I, or Br or any combination thereof.
Throughout the disclosure, references to the compounds of Formulas I, II, III, and IV are read as also including optical isomers and salts. Exemplary salts may include: hydrochloride, hydrobromide, hydroiodide, and the like. Additionally, the compounds of Formulas I, II, III, and IV may include tautomeric forms.
Certain compounds disclosed in this document can exist as one or more isomers. It will be appreciated by those skilled in the art that one isomer may be more active than the others. The structures disclosed in the present disclosure are drawn in only one geometric form for clarity, but are intended to represent all geometric and tautomeric forms of the molecule.
In one exemplary embodiment, a method of making compounds of Formula III is provided. The method includes contacting a compound of Formula II with an alkali alkoxide and an alkylating agent, and forming a compound of Formula III:

wherein R1 is selected from the group consisting of:
and
R2 is selected from the group consisting of:

In a more particular embodiment, the contacting step is carried out between 22° C. and 60° C.
In a more particular embodiment of any of the above embodiments, the contacting step further includes a solvent selected from the group consisting of DMF, DMSO, DMA, NMP, and CH3CN.
In a more particular embodiment of any of the above embodiments, the alkali alkoxide is selected from the group consisting of: KOtBu, CH3ONa, CH3CH2ONa, CH3CH2OLi, CH3OLi, CH3CH2OK, and CH3CH2ONa.
In a more particular embodiment of any of the above embodiments, the alkylating agent is selected from the group consisting of: alkyl halides and benzyl halides.
In a more particular embodiment of any of the above embodiments, the alkyl halide and benzyl halide are selected from methyl iodide (CH3I), ethyl iodide (C2H5I), and benzyl bromide (BnBr).
In a more particular embodiment of any of the above embodiments, the alkali alkoxide is KOtBu, and the solvent is DMF.
In a more particular embodiment of any of the above embodiments, a molar ratio of Compound II to alkali alkoxide is from about 3:1 to about 1:1 and a molar ratio of Compound II to alkylating agent is from about 1:1 to about 3:1. In an even more particular embodiment, a molar ratio of Compound II to alkali alkoxide base is about 2:1 a molar ratio of Compound II to alkylating agent is 1:3.
In a more particular embodiment of any of the above embodiments, the method includes diluting a completed reaction mixture with CH3CN and 2.5% aqueous Na2S2O3. In an even more particular embodiment, a ratio of DMF to CH3CN is from about 1:1 to about 3:1 and a ratio of DMF to 2.5% aqueous Na2S2O3 is from about 1:2 to about 2.1. In another more particular embodiment, a ratio of DMF to CH3CN is about 2:1 and a ratio of DMF to 2.5% aqueous Na2S2O3 is about 1:1.
In another embodiment, a method of preparing a compound of Formula II is provided. The method includes contacting a compound of Formula I with bis-N,O-trimethylsilylacetamide; and forming a compound of Formula II

wherein R1 is selected from the group consisting of:
and
R2 is selected from the group consisting of:

wherein a molar ratio of compound Ito bis-N,O-trimethylsilylacetamide (BSA) is 1:1.1. and the contacting step is carried out at about 22° C. to about 70° C.
In a more particular embodiment, the contacting step further includes contacting compound I with CH3CN. In another more particular embodiment, the method includes contacting a BSA treated reaction mixture with an arylsulfonyl chloride. In an even more particular embodiment, a molar ratio of Compound I to arylsulfonyl chloride is from about 1:2 to about 2:1, In another more particular embodiment, a molar ratio of Compound I to arylsulfonyl chloride is 1:1.1.
The embodiments described above are intended merely to be exemplary, and those skilled in the art will recognize, or will be able to ascertain using no more than routine experimentation, numerous equivalents of specific compounds, materials, and procedures. All such equivalents are considered to be within the scope of the invention and are encompassed by the appended claims.